It doesn't matter if they live for 2000 years and can spend another 2000 in suspended animation; the chances of anyone stumbling on our little rock are infinitessimal.
Who knows- maybe their home planet is a star like the sun, and the concept of planets made of things like soil and rock is infinitely fascinating to them. Who knows what the hell an alien would do? The other application for the word "alien" is for something foreign and unfamiliar. I hate to use a sci-fi show to prove my point, but it is a Star Trek forum. Despite McCoy's and Spock's insistance that something like a silicon-based life form absolutely cannot exist in "The Devil in The dark", they found one anyway.